1. Field of the Invention
The field of art to which this invention pertains includes that of transmission controls and more particularly to an improved resistance-producing structure for a manual shifting mechanism used with a mechanical transmission.
2. Description of the Prior Art
While manual shifting mechanisms for mechanical transmissions utilize a great variety of different designs and structures, they generally utilize a plurality of longitudinally shiftable members, such as shift rails or members associated therewith. Many of these structures utilize a shift lever unit that is mounted within a support housing and includes a shift lever bracket or gimbal that is mounted within the support housing for transverse rocking or pivoting movement on a longitudinal axis. Generally, a shift lever is carried by the gimbal for transverse movement therewith and is pivoted within the gimbal and relative thereto for longitudinal fore-and-aft shifting movement about a transverse axis. The shift lever and gimbal are swingable as a unit transversely on the longitudinal axis when the shift lever is vertical and the longitudinally shiftable members are centered, with the shift lever being swingable longitudinally on the transverse axis and including a downwardly projecting shift element for selectively engaging and longitudinally shifting each of the longitudinally shiftable members. A general structure of the type described hereinabove, but not restricted thereto, is shown and described in U.S. Pat. No. 3,667,105 to Dence (also assigned to the assignee of this invention).
It is also well known that overspeeding of the prime mover can occur by improper downshifting and that extensive damage to the transmission can occur by attempting to shift to reverse gear during forward motion. Thus, it is well known to provide the shifting mechanism with a resistance, which is felt by and must be overcome, by the operator when selecting, for example, first and/or reverse gear. The resistance-producing structure often takes the form of a plunger which is spring pressed outwardly so as to contact the shift lever and prevents accidental lateral movement of the shift lever unit into engagement with, for example, the first and/or reverse gear shift rail. Overcoming the resistance of the spring requires a conscious effort on the part of the operator and prevents accidental movement of the shift lever into the associated longitudinally shiftable member. A somewhat similar structure is shown in FIG. 5 of the above-referred to prior art patent.
While the prior art devices perform very satisfactorily, the addition of plungers, machined bores for containing plungers, as well as threaded elements associated therewith, make many of these prior art units expensive to manufacture and expensive to install. In addition, most of the prior art units are also overly-complicated for the simple function they are called upon to perform.